Chain saw



FIG. 1 is a rear perspective view of a chain saw showing my new design;

FIG. 2 is an elevational view of the side opposite that shown in FIG. 1;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a front elevational view thereof; and

FIG. 6 is a rear elevational view thereof. 

The ornamental design for a chain saw, substantially as shown. 